Minitaur Quadruped Robot Walks, Climbs Fences, Opens Doors

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September 23, 2016      

You’ve probably seen robots that walk, roll, climb and open doors. The Ghost Minitaur robot, however, does all of this in one package – a medium-sized quadruped walker that stands well under a half meter tall.

Built by Ghost Robotics, Minitaur can travel in a front-to-back orientation or at a slower, side-to-side orientation in which it rolls over itself in either direction. If that’s not impressive enough, Minitaur can also open doors with a “jump and swipe” maneuver and climb fences by carefully manipulating its powerful legs.

Minitaur does all of this with just four legs that each have two motors. The mechanical portion of Minitaur seems simple at first, but a closer look show it’s extremely well designed. Each leg system is offset at 5 degrees and is built as 5-bar linkage assembly. With this linkage setup, inputs from not one, but two motors combine to determine the final position of the legs. This allows the legs to be positioned nearly anywhere outside the body, only restricted by the length of the linkages and the possibility of physically hitting the robot’s chassis.

Photos: Meet Minitaur the Quadruped Robot

The impressive power that can be seen in Minitaur’s intro video, which you can watch above, is largely a function of the direct drive system. Unbelievably, Minitaur was built with off-the-shelf parts. And because it uses no gearbox between the motors, which would add extra inertia, backlash, and friction, the force “felt” by the legs can more easily be sensed by the control unit and used while moving. This feedback transparency is where the term “Ghost” comes from.

Minitaur currently is operated as a remote-controlled vehicle. The lower-level operations, such as how each motor needs to rotate at a certain instant and force feedback, is handled by the on-board processor, an STM32F series microcontroller that can be programmed in an Arduino environment. The control board also includes connections for a Raspberry Pi. An integrated ‘Pi could be used to handle higher-level control functions and research about how Minitaur can be further used, such as vision processing or more advanced control schemes.

Ghost Robotics Minitaur Quadruped Robot

What you see in the video, though truly impressive, is hopefully only the tip of the iceberg. Perhaps you may soon see a Minitaur autonomously bounding down your street or, perhaps more likely, a local university. On the other hand, if you’d rather not wait for this possible future, perhaps you can get started with your own robot using one of these popular platforms.

If Minitaur’s specs aren’t impressive enough, it’s worth noting that Ghost Robotics was founded by two PhD candidates, Avik De (electrical), and Gavin Kenneally (mechanical), who both studied at the University of Pennsylvania. As De puts it, “A PhD is a full time job, and we have to carve out time to work on the company, but our research interests align quite well with what we’re trying to do.” This gave them a sort of “double-sided motivation” that has allowed them to simultaneously research and develop technology for their company.

Ghost Robotics has been helped in its creation by the Penn Center For Innovation (PCI). In exchange for a stake in Ghost Robotics, PCI has helped gett this venture off the ground. According to Kenneally, “the university encourages the creation of these kinds of startups,” which would be a great resource for people with the “next big idea.”